Accelerator of vulcanization



Patented Dec. 19, 1939 UNITED STATES PATENT OFFICE ACCEPERATOR FVULOANIZATION Joy G. Lichty, Stow, Ohio, assignor to WingfootCorporation, of Delaware Wilmington, DeL, a corporation No Drawing.Application May'lfi, 1936, Serial No. 80,139

16 Claims. (01. 260 78s)- This invention relates tOthe process oftreating rubber and, more particularly, to the provsion of improvementsin the vulcanization of rubmary accelerators and the basic materialswhich 16 increase their accelerative power as activators or secondary orauxiliary accelerators, for most of the basic materials useful for thispurpose have some accelerative power in and of themselves.

Among such known auxiliary accelerators are 20 the activating aminessuch as dibenzyl amine, 2-4-diamino disphenyl amine, piperidine, benzylamine, etc. In many cases these activating amines have been undesirableas auxiliary accelerators because of their excessive scorching 25tendencies. By this it is meant that they tend to cause vulcanization atprocessing temperatures to such an extent that they are incapable of usein most rubber stocks which must undergo a certain amount of processing.In other cases they 30 may be incorporated uniformly in rubber only withdifficulty. Thus, some of the activating amines are too volatile topermit their use in their free form with any degree of success.

It is an object of this invention to provide 35 an improved process forvulcanizing rubber in the presence of two accelerators, one being aprimary organic accelerator and the other an auxiliary accelerator. Afurther object is to provide auxiliary accelerators prepared from ac- 40tivating amines in a form in which their tendencies to activate theprimary accelerator at milling and processing temperatures aresubstantially inhibited. Anotherobject is to provide such auxiliaryaccelerators in a form in which they 45 may be used in rubber compoundswith uniformity of results. Other objects will become apparent as thedescription of the invention proceeds.

riefiy, the invention comprises the discovery 55 Among the organicaccelerators those which are activatable are, of course,-useful in thepractice of the invention. Exemplary of such activatable organicaccelerators are the preferred primary accelerators of the invention,namely, the aromatic thiazyl, sulphide accelerators among 5 which aremercaptobenzothiazole, 5-nitro' l-mercaptobenzothiazole,di(benzothiazyl) disulphide, dibenzothiazyl mono sulphide, the mercaptonaphtha thiazoles, ethoxy carbonyl benzothiazyl sulphide, acetonylbenzothiazyl sulphide, benzoyl benzothiazyl sulphide, 2-4-dinitrophenylbenzo thiazyl sulphide, and the like. Other primary accelerators aretetra methyl thiuram disulphide, tetra methyl thiuram mono sulphide, dipenta methylene thiuram mono sulphide, 2-4-dinitro 1 phenyl dimethyldithiocarbamate, and other dithio carbamic acid esters such as acetonyldimethyl dithiocarbamate, carboxy methyl dimethyl dithiocarbamate andphenacyl diethyl dithiocarbamate; the xanthate accelerators such as zincIbutyl xanthate, etc. In general, these primary organic acceleratorswhich are useful in the invention are commonly known as ultra orsemi-ultra accelerators.

The auxiliary accelerators of the invention are, as stated previously,complex compounds of metal salts with activating amines. They aregenerally prepared by merely bringing the metal salt and the aminetogether, preferably in a liquid dispersion and generally in suspensionor solution in water. Apparently the reaction is simply one of addition.In certain cases, it is advisable to heat the reaction mixture toprovide a complete reaction between the materials. Usually the amine andmetal salt react in molecular proportions but in some cases two or threeor perhaps more mole of the amine add to one mol of the metal salt.Other dispersing agents such as alcohol, benzene, xylene and gasolinemay, of course, be used in place of water. 40

Among the metal salts which may be used in preparing the complexcompounds of the invention the zinc salts are preferred. Other salts arethose of the alkaliand alkaline earth metals,

and of magnesium, cobalt, nickel, antimony, aluminum, cadmium, bismuthand the like. Generally the bivalent metal salts will be preferred and,among these, the calcium and zinc salts, of which the zinc salts appearmost desirable.

' Further illustrative of metal salts. are the inorganic metal salts,the metal salts of carboxylic acids, the metal salts of dithiocarbamicacids, the metal salts of the mercaptobenzothiazoles, the metal salts ofdithio organic acids such as dithio fur oic and dithio benzoic acids. Ofthese,

the inorganic metal salts, the carboxylic acid metal salts and the metalsalts of dithiocarbamic acids derived from primary amines are preferred.The complex compounds obtained by reacting ing. During the reaction onlya very small amount of the solid material went into solution. The masswas then cooled and the solid filtered off. 103 grams of a colorlesssolid melting at amines with the zinc salts of dithiocarbainic acids atemperature higher than 280 C. and believed 5 derived from secondaryamines are in general to be the addition product of one mol of zinc suchpowerful accelerators that they may be oxalate and one mol of ethylenediamine were used by themselves as primary accelerators. It obtained.will be understood, however, that in certain trub- Errample 3 ber stocksthey will be found desirable as ac ival tors. Among the amines which maybe reacted t A of of Et f i with metal salts to form the complexcompounds mo 60 pmpmuons 0 0 of the invention are the primary amines,which crysaanlzatgon and grams of 057010116X? amme are preferred, and,among these, the saturated tonne by heatmg mixture of P t primary amineswhich are particularly desiraenas. on a hot plate a OI able; thesecondary amines of sufficient basicity Fnateml sepatated coohng whichi' to activate organic accelerators, and tertiary alimg and Washing Wlthf Obtained} m phatic amines. By the term activating amine an.amo'unt 45grams memng it is meant to include the organic amines which T product 15behgved to be the addltlon have the property of activating organicaccelerauct of one 9 of Zmc acetate a two molspl tors of vulcanization.These are well known in cyclohexylamme Its .average nitrogen and Zmc theart- In general these are primary amines, analyses were, respect1vely,7.56% and 17.8%, as Secondary amines of aliphatic characteristics andcompared with the theoretical nitrogenand zinc tertiary aliphatic aminesIt will be understood contents for the addition product of one mol ofthat the invention does not contemplate the zinc acetate and two mols ofcyclohexyl amine of use of complex salts of the amides and amidines 736%and 171%- as the amides and amidines are not amines. ple 4 Furtherillustrative of the invention are the In the preparation f anotherauxiliary accelfollowing examples: erator of the invention, 12.9 gramsof dibutyl Example 1 amine were dissolved in 50 cc. of petroleum etherand added to a suspension of 25 grains of zinc The addition product ofcyolohexyl amine and stearate in 150 cc. of petroleum ether. The mixzinocyclohexyl dithiocarbamate may be prepared ture was allowed to standovernight after which by adding a solution of 6 grams of cyclohexyl thepetroleum ether remaining was evaporated amine in petroleum ether to asuspension of 17.5 over a steam bath. The remaining mass was "3% gramsof zinc cyclohexyl dithiocarb-amate and then filtered hot and theprecipitate dried. 22 200 cc. of petroleum ether. The suspension wasgrams of a dry product melting at 102-106 C. stirred during the additionof the cyclohexyl and believed to be the addition product of molar aminesolution. This stirring was continued for p op o o Zinc Stearate anddibutyl amine a period of one hour after which the mass was Wereobtained. filtered and the resulting precipitate washed and Emample 5dried. The product was obtained in the form of a cream colored solidmelting over the range of gg z ggggg g? 2 :523 gggig gt l05-l25 C. andis believed to be the addition Zn NOB 23H2O with 25 5 gvgms 6 niperidineproduct of one mol of cyclohexyl amine and one warming mixture slightlyon a Steam mol of Zinc cyclohexyl dithiocarbama'te' An whereupon a viorous reaction takes place and average nitrogen analysis for thisproduct gave then cooling mixture an ion bath 8.55% as compared with thetheoretical nitrogen vent decomposition of the nitrat; All of thecontent of the addition product of one mol of zinc amine appears to havereacted on Washing cyclohexyl amine and zinc cyclohexyl dithiocarthemixture with 250 portins of petroleum bama'te of 820% ether andfiltering, only cc. of piperidine was Example 2 found in the filtrate.25.8 grams of a light yellow sticky solid melting at a temperature of155- In the preparation of another auxiliary accel- 160 C. wereobtained. ora 0f t e i v a mixture of /2 H101 Of Other illustrativeauxiliary accelerators of the Zinc oxalate d /2 H101 0f q e s ylinvention prepared in a similar manner are given diamine in 125 cc. ofwater was heated to boilin the following t bl TABLE I 60 Metal saltAdditive amine 35 3;355: 2 Product gggfiigt lth lvlgne itiainine 3az1mColorless solid Abo e 280 s iifyi$Z$t$nas11311111 tififi 3:13:33: T? 4Ethylene diamine 39.:lm d "375159 5 Zmc chloride... Oyclohexylamine fl23.11111 210 6 Zinc chloride Amyl primary amine 2az1m .-..-do. 118-122 7Zinc chloride... *High boiling amines... Yellow solid 8 Zinc chlorideTetrahydro inrfurylamine.. Colorless solid... 9 Zinc chloride Piperidinell-193 10 Zinc chloride Ethylene diamine 11 Zinc formate Piperidine Highboiling alkylene polyamines obtained in the preparation of ethylenediami'ne, principally diethylena triamine and trietliylene "[5 tetramme.

2,184,238 3 TABLE IContmued Melting or Molecular Metal salt Additiveamine proportions Product gggglgisg 12 Cobalt chloride Aniline 2a:1n1Blue solid 13 Zinc cyclohexyl dithiocarbamate. Piperidine 1a: 1m Whitesolid 95-110 14 Zinc cyclohexyl dithiocarbamate Butylamme 88-100 15 Zinctetrahydro furfuryl dtc Piper1d1ne 75-90 16 Zinc tetrahydro iurfuryldtc. Cyclohexylamme 105-115 17 Zinc benzyl dithiocerbamate Piperldine 270-85 18 Zinc benzyl dithiocarbamate Cyclohexylamine 99-102 19 Zincbenzyl dithiocarbamate D butylarmnau. 70-80 20 Zinc phthalate.P1per1dine 250 21 d Cyclohexylamine Above 295 22 Piperidine Cream solid103-109 23 Cyclohexylamine Granular sticky solid 1 Below 100 24Dibenzylaminem Granular sticky solid Below 100 25 Benzyl amine Lightcream solid 85-00 26 Piperidine H Sticky'solid'. r

27 Cyclohexylarninen" White solid 110-125 28 Dibutyl amine.- Stickysemi-solid 29 do .t Butylamine do 30 Zinc citrate Cyclohexylamlne. Whitesolid Above 295 31 ,do Butyl amine lazlm do 32 ,do Benzyl amme Soapysemi-solid 33 Zinc carbonate Oyclohexylamm White solid 158-165 34 Zincnitrate. Oyclohexyla nlne Tan solid 158-165 35 do Dibenzylamme Lightcream solid. Above 295 36 .do Dicyclohexylam Brown solid s 155-160 37 doBenzylamme, Yellow crumbly solid -100 38 do n Aniline .1 White solid-155 39 do Ethyl aniline Light brown solid s 210-212 40 do Diisoamylamine Yellow solid 159-161 dtc stands for dithiocarbamate.

In the third column a refers to the additive amine and m to the metalsalt;

While the molecular proportions have been given inmost instances, thesefigures are not definitely known in all cases to be the true or onlyproportions in which the amines and the metal salts may be combined inthe final products, although these are believed to be correct. Also, themelting points or decomposition points, as they may be called, of manyof the compounds have in general a fairly wide range. This is probablyfor the reason that after some of the heating, portions of the amine andmetal salt starting materials, resulting from dissociation, are presentwith the addition product. These melting points were conducted in thenormal atmosphere (open capillary tube).

In most cases nitrogen analyses of the complex compounds were obtained.Typical analyses are as follows:

TABLE 11 Zinc acetate-ethylene diamine Theoretical Found values forPercent N 19. 9'0, 20. 07 20.1 Percent zinc 15.88, 15.90 15. 68

Zmc acetate-cyclohexyl amine Theoretical Found values for- Percent N 7156, 7. 56 7; 36 Percent zinc 17.8 17. 1

Zinc cycloheazyl dithiocarbamatediamine-,

Zinc beneyl dithz'ocarbamate-dibutyl amine Theoretical Found values forPercent N 7. 53

thiazyl sulphide. Others are the amine addition I products of metalsalts of dithiocarbamic acids derived from secondary amines,illustrative of which are the cyclohexylamine, benzylamine-, piperidine,N-ethyl cyclohexylamine, ethylene butyl ethylene diamine additionproducts of zinc dimethyl dithiocarbamate. These amines may also bereacted with the zinc dithiocarbamates derivedfrom piperidine, dibenzylamine, dibutylamine, N-ethyl cyclohexyl amine, diarnyl amine and thelike. Other illustrative auxiliary accelerators of the invention are thediethanol amine and triethanol amine addition products of calciumbromide, sodium iodide, calcium chloride, calcium iodide, sodiumbromide, lithium chloride and potassium iodide. Still others are thecorreamylamine-, dibutyl amine-, and dispending mono ethanol amineand diand tri I propanol amine addition products of the alkaliand alkalineearth metal halides and other metal salts.

Other amines which may be added to metal Salts to form auxiliaryaccelerators of the invention are dipropyl amine, hexahydro 0-, orptoluidine, N-methyl cyclohexyl amine, N-methyl tetrahydro alphafurfuryl amine, N-ethyl tetrahydro alpha furfuryl amine, pipecoline,sym. dimethyl ethylene diamine, beta phenethylamine, heptyl amine, andmethyl propyl amine.

Illustrating the use of these auxiliary accelerators in thevulcanization of rubber 'are the following formulae in which thecompounds have been found suitable (parts refer to weight).

Formula A Formula B Formula C Smoked sheet rubber 100 parts 50 parts 100parts. Pale crepe rubber 50 parts" Zinc oxide 5 parts. 5 parts. Sulphur3 parts. 3 parts. Titanium oxlde. p 10 parts. Accelerator As indicated..As indicated As indicated.

Illustrative compounds of the invention were incorporated into separateportions of a rubber stock corresponding to one of the above formulaeafter which the various rubber stocks were vul-'- oanized for-varyingperiods of time and physical tests obtained. The results are as follows:

TABLE II Modulus kgs./cm. Cure in mins. at Ult. tens. Max. elong.

F. kgsJcm. in percent Meroaptobenzothiazole, 0.3 part; addition productof zinc oxalate and ethylene diamine, 0.2 part; Formula BMercaptobenzothiazole, 0.3 parts; addition product of zin and ethylenediamine, 0.2 part; Formula B Mercaptobenzothiazole, 03. part", additionproduct of cyclohexylamine and zinc benzyl dithiocarbamato, 0.2 part;Formula A Modulus kgsJcm.

Ult. tens. kgs./cm.

Max. elong.

Cure in mins. at

F. in percent Mcrcaptobenzothiazole, 0.3 part; addition product ofcyclohcxyl amine and zinc chloride, 0.2 part; Formula BMercaptobenzothiazole, 0.3 part; addition product of high boiling aminesand zinc chloride, 0.2 part; Formula 13 Mercaptobenzothiazole, 0.3 part;addition product of tetrahydro alpha furfurylamine and zinc chloride,0.2 part; Formula C Mercaptobenzothiazole, 0.3 part; addition product ofpiperidine and zinc chloride, 0.2 part; Formula C Mercaptobenzothiazole,0.3 part; addition product of ethylene diamine and magnesium sulphate,0.2 part; Formula B Mercaptobenzothiazole, 0.3 part; addition product ofcyclohoxylamine and zinc sulphate, 0.2 part; Formula 13Mcrceptobenzothiazole, 0.3 port; addition product of amyl amine and zincsulphate, 0.2 part; Formula B liiurcaptobonzothiazolc, 0.3 port;addition product of cyclohexyl amine and zinc acetate, 0.2 part; FormulaB lvlercaptobenzothiazole, 0.3 part; addition product of mixed amylprimary amines and zinc formate, 0.2 part; Formula CMercaptobenzothiazole. 0.3 part; addition product of aniline and cobaltchloride, 0.2 part; Formula C 2 011808 to H. R. Thies. The fourauxiliary accelerators and the three primary accelerators are identifiedin Table III as follows:

A-Addition product of zinc acetate and cyclohexyl amine (Ex. 3). B-Addition product of zinc chloride and cyclohexyl amine (No. 5 in TableI).

CAddition product of zinc sulphate and mixed primary amylamines (No. 3in Table I).

D-Addition product of zinc cyclohexyl dithiocarbamate and piperidine(No. 13 inTable I).

Captax-Mercaptobenzothiazole. AltaxDi(benzothiazyl) disulphide.

tor and an activator for said accelerator which is a complex compound ofzinc chloride and a saturated primary amine.

4. The process of accelerating the vulcanization of rubber whichcomprises vulcanizing rubber in the presence of a benzothiazyl sulphideaccelerator and an activator for said accelerator which is a complexcompound of a zinc salt with a saturated primary amine.

5. The vulcanizates obtained bythe process of claim 1.

6. The process of accelerating the vulcanization of rubber whichcomprises vulcanizing rubber in the presence'of an organic acceleratorfrom the Tuads-Tetra methyl thiuram dlsulphlde. group consisting ofultra and semi-ultra accelera- TABLE III Modulus Primary acc. Auxil. ace7 I UR kgJc g Clue tens. Index number mms. kg lam 01g. 7 Name Name 500%700% F. Percent.

0. 50 40/200 100 750 20 32 103 0. 30 0. 20 25 200 173 725 43 155 .04 0.30 0. 20 30 200 132 725 44 102 30 0. 30 0. 20 20 200 157 720 30 133 Lessthan 30 0. 30 0. 20 30 200 105 750 30 120 93 0. 50 40 275 130 750 30 97Over 180 0. 30 0. 20 20 275 100 725 40 145 Over 130 0. 30 0. 20 30 275174 720 45 102 Over 130 0. 30 0. 20 30 275 141 730 112 Over 130 0. 30 0.20 30 27 107 725 42 147 31 o. 15 240 195 725 47 172 4 s2 0. 15 0. 20 20240 197 775 30 134 02 0. 15 0. 20 20 240 204 770 37 133 04 0. 15 0. 2030 240 204 730 47 173 72 0.15 0.20 10 240 138 700 37 137 Less than 30the auxiliary accelerators of the invention activate or increase theaccelerative activity of the primary accelerator to a great extent. Theyare particularly valuable for use with benzothiazyl sulphideaccelerators. By this invention it is possible to use practically any ofthe activating amines without the attendant properties inherent in manyof them of being very difficult to mix uniformly with rubber. Also,their tendencies to activate the primary accelerators at processing andmilling temperatures are greatly inhibited. Furthermore, the toxicqualities of some of them are considerably prevented by their use in theform of the present invention.

While the preferred embodiments of the invention have been described indetail herein, it will be understood that the invention is not solimited but that various modifications may be made therein withoutdeparting from the spirit of the invention or from the scope of theappended claims. It is intended to cover, by suitable expression in theaccompanying claims, all features of patentable novelty inherent in theinvention.

-What I claim is:

l. The process of accelerating the vulcanization of rubber whichcomprises vulcanizing rubber in the presence of a benzothiazyl sulphideaccelerator and an activator-for said accelerator which is a complexcompound of a zinc salt with a primary amine.

2. The process of accelerating the vulcanization of rubber whichcomprises vulcanizing rubber in the presence of a benzothiazyl sulphideaccelerator and a complex compound of zinc chloride and tors and anactivator for said accelerator which is a complex compound of a metalsalt with an amine from the group consisting of primary which is acomplex compound of a zinc salt with I an amine from the groupconsisting of primary amines, secondary amines of aliphaticcharacteristics and tertiary aliphatic amines.

8. The process of accelerating the vulcanization of rubber whichcomprises vulcanizing rubber in the presence of an organic acceleratorfrom the group consisting of ultra and semi-ultra accelerators and anactivator for said accelerator which is a complex compound of zincchloride and cyclohexyl amine.

9. The process of accelerating the vulcanization of rubber whichcomprises vulcanizing rubber in the presence of a benzothiazyl sulphideaccelerator and an activator for said accelerator which is a complexcompound of a metal salt with an amine from the group consisting ofprimary amines, secondary amines of aliphatic characteristics andtertiary aliphatic amines.

10. The process of accelerating the vulcanization of rubber whichcomprises vulcanizing rubber in the presence of a benzothiazyl sulphideaccelerator and an activator for said accelerator which is a complexcompound of a zinc salt with an amine from the group consisting ofprimary amines, secondary amines of aliphatic'characteristics andtertiary aliphatic amines.

in the presence of an organic accelerator from the group consisting ofultra and semi-ultra accelerators and an activator for said acceleratorwhich is a complex compound of a metal salt of an inorganic acid with anamine from the group consisting of primary amines, secondary amines ofaliphatic characteristics. and tertiary aliphatic amines.

12. The process of accelerating the vulcanization of rubber whichcomprises vulcanizing the rubber in the presence of a thiazyl sulphidevulcanization accelerator and an activator for said accelerator which isa complex compound of a metal salt of a dithiocarbamic acid derived froma primary amine with an amine from the group consisting of primaryamines, secondary amines of aliphatic characteristics and tertiaryaliphatic amines.

13. The process of accelerating the vulcanization of rubber whichcomprises vulcanizing the rubber in the presence of a thiazyl sulphidevulcanization accelerator and an activator for said 15. The process ofaccelerating the vulcaniza-.

tion of rubber which comprises vulcanizing rubber in the presence of anorganic accelerator from the group consisting of ultra and semi-ultraaccelerators and an activator for said accelerator which is a complexcompound of a zinc salt and cyclohexylamine.

16. The vulcanizates obtained by the process of claim 6.

JOY G. LICHTY.

